Circuit breaker with wide opening contacts

ABSTRACT

The circuit breakers involved are of the type having a contact arm pivoted between its ends and operable by a manually erected toggle for closing the contacts. A bell-crank, pivoted to one end of the contact arm, has a latch arm restrained by an over-current latch also carried by the contact arm. That type of circuit breaker is given increased interrupting capability by modification of its component parts, especially the handle and the linkage operated by the handle, to produce greatly increased contact separation.

United States Patent DeTorre I June 4, 1974 CIRCUIT BREAKER WITH WIDEOPENING 3.134.871 5/1964 Norden 200/145 x 3.464.040 8/1969 Powell 1 r335/l9l CONTACTS 3.599.136 8/l97l DeTorre.... 337/71 [75] Inventor: JohnDeTorre, Albemurle, NC. 3.6IO.856 10/1971 DeTorre 200/153 0 AssigneezFederal Pacific Electric p y, 162L189 ll/l97l, Lmk Z\()0/l53 G k, NJ.Newar Primary Examiner-A. T. Gnmley [22] Filed: Dec. 22, 1972 [2]] Appl.No.: 317,754 [57] ABSTRACT The circuit breakers involved are of the typehaving a 52 us. c1 337/59, 335/191, 337/13. Contact am pivoted betweenits ends and Operable y 7 7 a manually erected toggle for closing thecontacts. A 1511 Im. c1. 110111 71/16 bell-Crank, pivoted to one end ofthe Contact arm, has [58] Field f Search 7 3 36 37 5 7 a latch armrestrained by an over-current latch also 337/71, 72, 75 5 53 G carriedby the contact arm. That type of circuit breaker is given increasedinterrupting capability by [56] References Cited modification of itscomponent parts,.especially the UNITED STATES PATENTS handle and thelinkage operated by the handle, to produce greatly increased contactseparation. 2.733.312 l/l956 Christensen 337/110 X 2.876.308 3/1959 4Claims, 5 Drawing Figures Christensen 337/] H) X ing and the closedconditions of the circuit breaker,

and a manual toggle drives the movable contact closed as the togglebecomes erect and slightly over-set. De-

spite the continued efforts over the years to improve the circuitbreaker, to impart increasedinterruption capacity without proportionalincrease in dimensions of the mechanism and the enclosure, increasedinterruption capacity remained a problem.v This type of circuit breakeris exemplified by U.S. Pat. No. 2,700,713 issued .Ian. 25, 1955 to T. M.Cole et a]. Earlier forms of that circuit breaker are shown in U.S. Pat.No. 2,647,186 issued July 28, 1953 to T. M. Cole, U.S. Pat. No.2,459,427 issued Jan. 18, 1949 to H. A. Humpage and U.S. Pat. No.2,209,310 issued July 30, 1940 to P. M. Christensen. In U.S. Pat. No.2,700,713, the arc chute (where interruption of the arc takes placeduring opening of the contacts) is formed of parts that are intrememeasures represented in U.S. Pat. No. 3,134,871

issued May 26, 1964 to A. R. Norden met with limited success,particularly with respect to dependable interruption at higher voltagesand with increased available current.

Circuit breakers of this type as produced heretofore provide acontact-opening travel of approximately fivesixteenth of an inch. Anobject of the present invention resides in greatly increasing thecontact-opening travel of such a circuit breaker without correspondinglyenlarging the parts. In a practical form of circuit breaker madepursuant to the present invention, a contactopening travel offive-eighth of aninch has been realized without changing the size of thecontact arm or the bell-crank, by improvements that will be pointed outin greater detail in discussing the illustrative embodiment of thepresent invention that is shown in the accompanying drawings anddescribed in detail below. Through the present invention, areinterruption has been achieved with a single-pole circuit breaker incircuits having an available short-circuit current of 10,000 amperes ina 277-volt alternating current distribution line.

In the drawings:

FIG. I is a lateral view of a presently preferred embodiment of theinvention, showing a circuit breaker in its closed configuration, thecover of the two-part enclosure being removed and certain parts beingshown in cross-section for clarity;

FIG. 2 is a fragmentary view of the circuit breaker of FIG. 1 with themechanism shown in the position it would assume following over-currentrelease with the operating handle held in the on" position;

FIG. 3 is a fragmentary view of the circuit breaker of FIG. 1 withcontacts open and the handle in the off" position;

FIG. 4 is a fragmentary perspective view illustrating part of theoperating linkage of the circuit breaker of FIGS. 1 to 3; and

FIG. 5 is a cross-sectional view along the broken section line 5-5 inFIG. 4.

Referring now to the drawings, the circuit breaker as shown includes anenclosure formed of two parts and 11 of molded insulation. Screwterminal 12 includes a part 12a that carries a stationary contact 14which acts as a companion contact to movable contact 16. Movable contact16 is united to elongated contact arm 18, ordinarily a copper alloy forhigh conductivity. Contact arm 18 is povited near its center on ahelical coil spring 20 whoseaxial ends are received in bearing cavitiesin the opposite side walls of the insulating enclosure 10, ll.

Bimetal 22 and magnetic yoke 24 are united to contact arm 18 by anintegral rivet 18a. Armature 26 is carried by yoke 24 on pivot 26a andis biased counter-clockwise (as viewed-in FIG. 1) by a leaf spring 28,shown in greater detail in U.S. Pat. No. 3,599,136. Armature 26 has adependingportion 26b in which there is a cut-out, andbimetal '22 extendsthrough that cutout. A transverse ledge at the bottom of the'cut-out isbiased upward against a small piece of insulation 30 which is suitablyretained in the assembled position shown. Spring 28 biases the ledge ofarmature 26 upward against insulator 30.

Extending from bimetal 22 is a flexible braid 32 as of fine strands ofcopper wire, extending to a terminal 34.

I In the closed condition of the circuit breaker, a circuit can betraced from terminal 12 through contacts 14 and 16, along contact arm18, bimetal 22, and along braid 32 to terminal 34.

A so-called bell-crank 36 is carried on pivot 36!) in the end of contactarm 18 remote from contact 16 and has a latch arm which end 36a abuttingagainst the end of armature 26 forms a latch for restraining thebellcrank when the circuit breaker is closed. Armature 26 and bimetal 22and yoke 24 form an over-current release for the circuit breaker, inthat sudden extreme values of overload current cause armature 26 to beattracted downward and out of the (clockwise) path of latch arm end 36a.For moderate overloads of prolonged duration, bimetal 22 flexes downwardand draws armature 26 down and out of the path of latch arm end 36a.Accordingly, armature 26 and its control elements 22 and 24 constitutean over-current release.

A manual operator 38 has a hand lever 40 and is operable about astationary metal pivot pin 42 whose ends are received in bearings in thetwo sidewalls l0 and 11 of the insulating enclosure (FIG. 5). Coilspring 44 (also called the push-off" spring) is compressed between aprojection 46integral with manual operator 38 and a projection ofcontact arm 18. It biases contact arm 18 counter-clockwise about pivot20, the contactopening direction. When manual operator 38 has beenshifted clockwise, partway toward the opposite extreme from that shownin FIG. 1, projection 46shifts to the left and then spring 44 exertsclockwise bias on manual operator 38. This bias tends to rotate themanual operator clockwise about pivot 42, as viewed in FIG.

A metal member 48 is received snugly in recesses in manual operator 38and is held in assembly to operator 38 by pivot pin 42, forming a fixedpart of the manual operator. Hand lever 40 and member 48 areapproximately opposite each other in relation to the axis of pivot 42. Aconnecting link 50 has a pair of pins 52 and 54 in members 48and 36,respectively. When the circuit breaker is closed, (FIG. 1) pin 52 islocated slightly above a straight line between pivot 42 and pivot 54and, consequently, member 38, 48 and connecting link 50 constitute atoggle which is slightly overset. In turn, pivot 54 is located slightlyabove a straight line between the centers of pivot 52 and pivot 36b. Anythrust along the line between pivots 52 and 54 produces a clockwise biason bell-crank 36 urging the latch arm end 360 against the end ofarmature 36., b

When the circuit breaker is open, as shown in FIG. 3, the hand lever 40rests against a portion a of the enclosure, being biased into thatposition by coil spring 44. Correspondingly, contact arm 18 is biasedcounterclockwise about spring pivot so that contact arm 18 is pressedagainst a stop 10b of the enclosure. In this condition of the circuitbreaker, coil-spring pivot 20 is substantially straight, end to end.

. When the circuit breaker is to be closed, manual operator 38 is movedcounter-clockwise. Member 48 drives connecting link 50 so thatbell-crank 36 swings until its latch arm end 36a is arrested by armature26. Thereafter, bell-crank 36, armature 26 and contact arm 18 act as alatched triangular unit, in'the further closing operation of the circuitbreaker, driving contact arm 18 clockwise about pivot 20. Movablecontact 16 engages the companion contact 14 at a time when member 48 hasstill some distanceto move before assuming the position in FIG. 1. Whencontacts 14 and 16 engage, pivot 52-is well below a straight linebetween pivots 42 and 54. Further counter-clockwise operation of handlever 40 tends to erect. parts 48 and 50 which act as an operatingtoggle for the circuit breaker mechanism. During this erection of thetoggle, contact arm 18 is forced clockwise about its contact 16 as afulcrum. During this motion spring pivot 20 becomes stressed so that themid-portion of that spring which carries contact arm 18 shifts downwardrelative to the ends of the spring pivot seated in cavities in oppositewalls 10 and 11 of the insulating enclosure. During this motion,considerable contact pressure develops. Spring pivot 20 accommodatesover-travel of the operating linkage, after the contacts have come intoengagement. As is well known, pivot 20 might be replaced by a rigid pinand then companion contact 14 could be made movable and spring-biasedtoward contact 16 as one of several other ways of providing forover-travel".

An arcrunner 56 of iron has one end adjacent to and touching contact 14.A series of iron arc-splitter plates 58 below are runner 56 are suitablyheld in mutually spaced relationship. Plates 58 are U-shaped, so thatthe contact 16 cam move between the legs of each U as contact arm 18moves toward stop l0b.

In the event of an overload, such that armature 26 is drawndownward,either by magnetic attraction toward magnetic yoke 24 or as theresult of downward deflection of bimetal 22 due to over-current flowingthrough the circuit breaker, bellcrank 36 is no longer restrained.Spring 20 immediately drives contact arm 18 upward about contact 16 as afulcrum. As this occurs, bell-crank 36 moves clockwise through asubstantial angle. This clockwise motion of bell-crank 36 continues aspush-off spring 44 starts to drive contact arm 18 counterclockwise fordriving contact 16 away from contact 14 and toward its fully openposition.

An arc is drawn between contacts 14 and 16, and shifts along arc runner56. The are expands toward the left-hand ends of the arc splitterplates. The are is cooled and hot gases are emitted through wire meshwhich is disposed across vent opening 62. During the contact-openingoperation, contact arm 18 is guided between suitable bosses in thehousing, including boss 10c.

Referring now to FIGS. 4 and 5, certain details will be described thatare of controlling importance to the full realization of the objects ofthe invention. Bell crank 36 that is formed of sheet-metal includes apair of, opposite side portions 360 and 36d that may be called parts orstrips disposed and operable in parallel planes at opposite sides ofcontact arm 18. A bridge portion 36e extends opposite the end of contactarm 18 (but spaced therefrom) and interconnects and unifies strips 36cand 36d of the bell-crank. These parts 36c,

36d and 36e are all formed of a'single piece of sheetmetal.

Connecting link 50 is also formed of a single piece of sheet-metalincluding a side portion oppositeparts or strips 50a and 50b inspaced-apart parallel planes. Strips 50a and 50b are integral with aninterconnecting bridge portion 500. By like token, part 48 is formed ofa single piece of sheet-metal including a pair of strips 48a and 48bunited by an integral interconnecting bridge portion 48c.

Parts48a and 48b are separated from each other by a distance that islarge enough to receive strips 50a and 50b between them. Interconnection480 is at the side of parts 48a and 48b remote from member 50 in theopen condition of the circuit breaker mechanism as shown in FIG. 3.Consequently, a large portion of connecting link 50 is received betweenor straddled by strips 48a and 48b when the circuit breaker is open andthe handle is-in the ofF position (FIG. 3). By like token, parts 360forming the operating arm and 36d of the bellcrank fit between strips50a and 50b in the condition of the circuit breaker represented in FIG.2, that is, when the circuit breaker has tripped open in response to anoverload while the handle is held in the on position. In this sameposition, there is no possibility of interference between parts 48a and48b with the parts 36c and 36d of the bellcrank since the latter aremuch closer to each other than strips 48a and 48b. Finally, again in theposition'of FIG. 2, it is noted that interconnection 36c of thebell-crank is disposed at a place where it is free of interference withany other part of the circuit breaker mechanism in all conditions ofoperation. FIGS. 1, 2 and 3. Notably, while bell-crank 36 has two stripsand provides a stable forceresisting structure on contact arm 18 forerecting the toggle, nevertheless the latch arm end 36a of thebell-crank is free to'move alongside the contact arm (FIG. 2) when thisbecomes necessary as in FIG 3. By virtue of these relationships betweenthe operating links of the circuit breaker, it becomes possible tolocate stop 10b so far from contact 14 that roughly double the previouscontact-separation is obtained with the described mechanism as comparedwith the prior art commercially standard mechanism represented forexample in US. Pat. No. 2,700,713. The described linkage is symmetricalabouta central vertical plane in FIG. 5, so that no torsion forcesdevelop in transmitting the contact-closing effort from handle 40 tocontact arm 18. No lateral thrust develops in this operation. Moreover,the parts nest in one another, for achieving greatest collapse of thelinkage, which become necessary in the condition of FIG. 3.

Manual operator 38 is shaped specially to accommodate operation ofhandle 40 through an unusually long are. This motion is needed foroperating contact arm 18 through an increased angle, the contact-openingtravel of contact arm 18 being greatly increased to achieve increasedinterruption ratings. The large angle of operation of handle 40 isrealized, handle strength is preserved, and operating space for thelinkage is made available (see especially FIG. 5) for accommodating thewide contact separation critically needed for'high interruption ratings.Hand lever 40 extends from the large-radius portion 38b adjacent to asmall-radius portion 38a of the manual operator. The small-radiusportion 38a is adjacent the operating linkage when the breaker is openand the hand lever is at the off stop. A large label OFF is provided onportion 38b and is exposed when the breaker is open and the parts are inthe position of FIG. 3. Housing portions 100 and c cooperate with manualoperator portions 38a and 38b, respectively, to confine hot gases thatdevelop as a result of arcing. Beads 380 on the operator 38 are receivedin grooves in the housing, for confining the hot gases. Accordingly, theproportions of the manual operator 38 and hand lever 40 as shown in thedrawing represent a strong handle and the casing cooperates with themanual operator to confine arc-generated hot gases, and yet the linkageis capable of assuming either of the positions in FIG. 2 or FIG. 3 withthe contact arm in its unusually wide-open position as shown. All thedesired practical properties of the prior-art type of circuit breakerare preserved in the illustrative novel breaker, and yet itsinterruption rating is greatly increased.

The foregoing represents an exemplary embodiment of the invention, butvariations will be introduced by those skilled in the art, so that theinvention should be construed broadly in accordance with its full spiritand scope.

l claim:

1. A circuit breaker of the type having an elongated contact arm pivotedbetween its first and second ends and operable in a central planeperpendicular to the pivoted axis thereof, a movable contact carried bysaid first end of said contact arm and a companion contact engageable bysaid movable contact in the closed condition of the circuit breaker, abell-crank having a latch arm and an operating arm, and means forming afirst pivot between said arms of said bell-crank and carrying thebell-crank on said second end of said contact arm, overcurrent releasemeans carried by said contact arm and including a latch engageable bythe latch arm of said bell-crank for arresting said bell-crank againstpivoting relative to said contact arm, said bell-crank and said contactarm and said overcurrent latch forming a latched unit in the closing andclosed condition of the having a stationary second pivot and movablebetween an ON" position and an OFF position for closing and opening thecontacts, said push-off spring also biasing the manual operator towardits OFF" position when the contact arm is in its open position, aconnecting link, a third pivot connecting said connecting link to saidmanual operator, a fourth pivot connecting said connecting link to theoperating arm of said bell-crank, all of said pivots having parallelaxes perpendicular to said central plane, said manual operator and saidconnecting link forming a toggle for driving said latched unit in thecontact-closing direction and for holding the contacts closed subject tocontrol by said latch, characterized in that said operating arm of saidbell-crank includes side portions disposed at opposite sides of saidcontact arm and a bridge portion interconnecting and unifying said sideportions, both of said side portions bearing said fourth pivot, and saidside portions acting on said contact arm via said first pivot meanssymmetrically with respect to saidcentral plane, further characterizedin that said latch arm of the bell-crank is free of transverse structurethat could impede movement thereof alongside the contact arm, foraccommodating relatively wide separation of said movable contact fromsaid companion contact 2. A circuit breaker as claimed in claim 1,wherein said. connecting link comprises side portions straddling theside portions of the bell-crank and a bridge portion interconnecting andunifying the side portions of the connecting link and wherein the sideportions of said connecting link are free of transverse structure thatcould impede collapsing movement of said connecting link and saidbell-crank as said latch arm moves into position alongside the contactarm when said manual operator is in its ON" position, thereby allowingtravel of the contact arm to its full open position.

3. A circuit breaker as claimed in claim 1, wherein said manual operatorcomprises side portions straddling the side portions of the connectinglink, both of said side portions of the connecting link bearing saidthird pivot, said side portions of said manual operator bearing on saidthird pivot symmetrically with respect to the central plane for applyinga balance operating force to said connecting link, and wherein the sideportions of said manual operator are free of transverse structure thatcould impede collapsing movement of said manual operator and saidconnecting link when the movable contact moves to its fully openposition, following release of said bell-crank by the over-currentrelease means, thereby allowing return of said manual operator to itsOFF" position.

4. A circuit breaker of the type having an elongated contact arm pivotedbetween its first and second ends and operable in a central planeperpendicular to the pivotal axis thereof, a movable contact carried bysaid first end of said arm and a companion contact engageable by saidmovable contact in the closed condition of the circuit breaker, abell-crank having a latch arm and an operating arm, a first pivotbetween said arms of said bell-crank and carrying the bell-crank on saidsecond end of said contact arm, over-current release means carried bysaid contact arm and including a latch engageable by said latch arm ofsaid bell-crank for arresting said bell-crank against pivoting relativeto said contact arm, said bell-crank and said contact arm and saidover-current latch forming a latched unit in the closing and closedcondition of the contacts, a push-off spring biasing said contact armaway from said companion contact, a manual operator having a stationarysecond pivot and movable between an ON position and an OFF position forclosing and opening the contacts, a connecting link, a third pivotconnecting said connecting link to said manual operator, a fourth pivotconnecting said connecting link to said operating arm of saidbell-crank, all of said pivots having parallel axes, said manualoperator and said connecting link forming a toggle for driving saidlatched unit in the contact-closing direction and for holding thecontacts closed subject to control by said latch, characterized in thatsaid manual operator and said connecting link and ing force to thebell-crank.

1. A circuit breaker of the type having an elongated contact arm pivotedbetween its first and second ends and operable in a central planeperpendicular to the pivoted axis thereof, a movable contact carried bysaid first end of said contact arm and a companion contact engageable bysaid movable contact in the closed condition of the circuit breaker, abell-crank having a latch arm and an operating arm, and means forming afirst pivot between said arms of said bell-crank and carrying thebell-crank on said second end of said contact arm, overcurrent releasemeans carried by said contact arm and including a latch engageable bythe latch arm of said bell-crank for arresting said bell-crank againstpivoting relative to said contact arm, said bell-crank and said contactarm and said overcurrent latch forming a latched unit in the closing andclosed condition of the contacts, a pushoff spring biasing said contactarm away from said companion contact, a manual operator having astationary second pivot and movable between an ''''ON'''' position andan ''''OFF'''' position for closing and opening the contacts, saidpush-off spring also biasing the manual operator toward its ''''OFF''''position when the contact arm is in its open position, a connectinglink, a third pivot connecting said connecting link to said manualoperator, a fourth pivot connecting said connecting link to theoperating arm of said bell-crank, all of said pivots having parallelaxes perpendicular to said central plane, said manual operator and saidconnecting link forming a toggle for driving said latched unit in thecontact-closing direction and for holding the contacts closed subject tocontrol by said latch, characterized in that said operating arm of saidbell-crank includes side portions disposed at opposite sides of saidcontact arm and a bridge portion interconnecting and unifying said sideportions, both of said side portions bearing said fourth pivot, and saidside portions acting on said contact arm via said first pivot meanssymmetrically with respect to said central plane, further characterizedin that said latch arm of the bell-crank is free of transveRse structurethat could impede movement thereof alongside the contact arm, foraccommodating relatively wide separation of said movable contact fromsaid companion contact.
 2. A circuit breaker as claimed in claim 1,wherein said connecting link comprises side portions straddling the sideportions of the bell-crank and a bridge portion interconnecting andunifying the side portions of the connecting link and wherein the sideportions of said connecting link are free of transverse structure thatcould impede collapsing movement of said connecting link and saidbell-crank as said latch arm moves into position alongside the contactarm when said manual operator is in its ''''ON'''' position, therebyallowing travel of the contact arm to its full open position.
 3. Acircuit breaker as claimed in claim 1, wherein said manual operatorcomprises side portions straddling the side portions of the connectinglink, both of said side portions of the connecting link bearing saidthird pivot, said side portions of said manual operator bearing on saidthird pivot symmetrically with respect to the central plane for applyinga balance operating force to said connecting link, and wherein the sideportions of said manual operator are free of transverse structure thatcould impede collapsing movement of said manual operator and saidconnecting link when the movable contact moves to its fully openposition, following release of said bell-crank by the over-currentrelease means, thereby allowing return of said manual operator to its''''OFF'''' position.
 4. A circuit breaker of the type having anelongated contact arm pivoted between its first and second ends andoperable in a central plane perpendicular to the pivotal axis thereof, amovable contact carried by said first end of said arm and a companioncontact engageable by said movable contact in the closed condition ofthe circuit breaker, a bell-crank having a latch arm and an operatingarm, a first pivot between said arms of said bell-crank and carrying thebell-crank on said second end of said contact arm, over-current releasemeans carried by said contact arm and including a latch engageable bysaid latch arm of said bell-crank for arresting said bell-crank againstpivoting relative to said contact arm, said bell-crank and said contactarm and said over-current latch forming a latched unit in the closingand closed condition of the contacts, a push-off spring biasing saidcontact arm away from said companion contact, a manual operator having astationary second pivot and movable between an ''''ON'''' position andan ''''OFF'''' position for closing and opening the contacts, aconnecting link, a third pivot connecting said connecting link to saidmanual operator, a fourth pivot connecting said connecting link to saidoperating arm of said bell-crank, all of said pivots having parallelaxes, said manual operator and said connecting link forming a toggle fordriving said latched unit in the contact-closing direction and forholding the contacts closed subject to control by said latch,characterized in that said manual operator and said connecting link andsaid bell-crank individually comprise side portions operable inrespective planes parallel to the central plane and symmetrical thereto,the side portions of said bell-crankbeind disposed at opposite sides ofsaid contact bell-brank being at said first pivot, the side portions ofsaid connecting link straddling said operating arm of said bell-crank,and the side portions of said manual operator straddling said connectinglink at said third pivot, so as to enable the manual operator in movingtoward its ''''ON'''' position to apply a symmetrical driving force tothe bell-crank.